Co₃O₄ nanospheres with a mean diameter of 19 nm were applied in the selective oxidation of 2-propanol to acetone in the gas phase. Compared with 9 nm spheres, the 19 nm spheres exhibited superior catalytic activity and stability with 100% selectivity to acetone up to 500 K. Transmission electron microscopy, N₂ physisorption, 2-propanol and O₂ temperature-programmed desorption, and 2-propanol temperature-programmed surface reaction in O₂ were applied to characterize the bulk and surface properties. Despite the smaller specific surface area (35 m² g⁻¹), an increased 2-propanol adsorption capacity was observed for the larger nanospheres ascribed to a preferential (110) surface orientation. Temperature-programmed oxidation experiments after reaction showed multilayer coke deposition and severe reduction of the Co₃O₄ surface, but excellent stability was maintained at 430 K using the 19 nm spheres in a steady-state oxidation experiment for 100 h with only 10% loss of the initial activity. The good agreement of the 2-propanol decomposition profiles indicates that the superior activity is caused by the enhanced interaction of the larger nanospheres with O₂. A Mars–van Krevelen mechanism on the (110) surface was identified by density functional theory calculations with a Hubbard U term, favoring faster reoxidation compared with the (100) surface predominantly exposed by the 9 nm spheres.

中文翻译：

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粒径对 Co3O4 纳米球选择性 2-丙醇气相氧化的影响

平均直径为19 nm的Co ₃ O ₄纳米球用于在气相中将2-丙醇选择性氧化为丙酮。与 9 nm 球相比，19 nm 球表现出优异的催化活性和稳定性，对丙酮的选择性高达 500 K。 透射电子显微镜、N ₂物理吸附、2-丙醇和 O _{2 程序}升温脱附以及 2-丙醇O ₂中的程序升温表面反应被用于表征体积和表面性质。尽管比表面积较小 (35 m ² g ^-1)，由于优先的 (110) 表面取向，观察到较大的纳米球的 2-丙醇吸附容量增加。反应后的程序升温氧化实验显示多层焦炭沉积和 Co ₃ O ₄表面的严重还原，但在 430 K 下使用 19 nm 球体在稳态氧化实验中保持了 100 小时的优异稳定性，仅损失 10%最初的活动。2-丙醇分解曲线的良好一致性表明优异的活性是由较大的纳米球与O ₂的增强相互作用引起的。使用 Hubbard U 的密度泛函理论计算确定了 (110) 表面上的 Mars-van Krevelen 机制 术语，与主要由 9 nm 球体暴露的 (100) 表面相比，有利于更快的再氧化。